Antioxidant defense and funtional integrity of acrosomal membrane during ram sperm cryopreservation

QUINTANA M.M; MEDINA V.; AISEN E; MORELLO H; AVELDAÑO, M.I; CORONEL C; VENTURINO A

San Carlos de Bariloche

Congreso; XXXIX Reunión Anual de la SAIB; 2003

SAIB

Thawing of cryopreserved ram semen currently enhances reactive oxygen species accelerating semen aging. We have developed hypertonic diluents which result better cryoprotectants evaluated in vitro and in vivo, and inversely related to lipid peroxides. We compare here glutathione (GSH) content and GSH reductase (GR) activity in spermatozoa, and in vitro capacitation and acrosome reaction after freeze-thawing in isotonic (B1) vs. hypertonic diluents containing threalose (B2) or threalose+EDTA (B3). GSH content was significantly lower in spermatozoa frozen in B1 (p=0.05), and 3h after thawing (p=0.015). GR activity was significantly decreased using B1 (P=0.00008) and 3h after thawing (p=0.013). Intact acrosomes were significantly lower using B1 when thawing in control medium (p<0.0007), with a high capacitation percentage (72%) which was lower for B2 and B3. Capacitation with seroalbumin increased acrosome reaction downshifting intact acrosomes, and additionally from capacitated ones in B1. Ca 2+ ionophore A23187 increased reacted status to 60% for B2 and B3 decreasing capacitation to 34%. These results suggest that the notable capacitation by freeze- thawing would be lower for semen cryopreserved in hypertonic diluents, maintaining besides a better response to chemical signals for acrosome capacitation and reaction. A better antioxidant status is inferred from GSH and GR which may be related to this action